As millions ready to hit the road for the holidays, motoring club says gas costs 20 cents more per gallon than same time in 2016.

The national average for a gallon of gasoline is $2.43, down 3 cents from a week ago, 12 cents less than a month ago but 20 cents more expensive than a year ago.

That's according to AAA's weekly calculations. The motor and travel club on Monday said that motorists in the Midwest are seeing the biggest declines, with prices in the region down as much as 10 cents.

Prices rose from a week ago in two states, increasing 3 cents in Indiana and a penny in Hawaii.

“More than 97 million Americans will begin to hit the road this week for the holidays – the most ever,” Jeanette Casselano, AAA spokesperson, said. “Today, motorists can find gas for $2.50 or less at 71 percent of gas stations in the country.”

The states with the biggest yearly changes include Alaska, where prices are up 54 cents from this time last year, and California, where motorists are paying 43 cents more than a year ago. In Montana, gas prices are 42 cents higher than in 2016, and in Oregon, drivers are paying 38 cents more, on average.

The least costly gas can be found in Missouri, where a gallon averages $2.16, and South Carolina, Alabama, Oklahoma, Mississippi and Texas, where it's $2.18, according to AAA.